Search

Eight oats catch crop trials were conducted over two years on winter forage paddocks on commercial dairy farms in Canterbury and Southland measuring the effect of tillage and timing-by-tillage, respectively, on dry-matter (DM) yields, N uptake and profitability (gross profit margin). The main objective was to successfully integrate catch crops into winter forage rotations over a critical period when the soil is normally bare and the potential for N drainage loss from urinary-N deposition is high. Oat harvest yields at green-chop silage maturity (∼50% panicle emergence) ranged from 8 to 10 t DM/ha when sown by the end of winter (4–5 months after drilling). Nitrogen uptakes ranged from 52 to 363 kg N/ha. Net gross profit typically ranged from NZ$1000 to NZ$1600/ha (assuming revenue of NZ$0.20/kg DM for standing feed). Minimum-till cultivation produced higher DM yields than direct-drill treatments in both years of the Canterbury trials (∼30% higher overall) but where N availability and good soil-seed contact were maintained, differences in yield were small (∼5%). Earlier sowing in Southland using a spader-drill combination increased DM yields and N uptake overall by 123% and 48%, respectively, over later sown conventional tillage options. [ABSTRACT FROM AUTHOR]

Residual nitrogen (N) left in the soil following summer cropping or grazing by livestock is at risk of leaching in winter and spring. This study, conducted in Waikato, New Zealand, assessed the performance of different catch crop species and sowing dates in reducing the risk of N leaching. In 2016, Italian ryegrass and oats were sown in late March, April and May. In 2017, Italian ryegrass, oats and triticale were sown in mid March, April and May. In both years, urea fertiliser (400 kg N/ha) was applied immediately before the first sowing to simulate high N loading of the soil following crop grazing. Both years also included a fallow treatment (control) in which no catch crops were established. In both years, catch crops reduced N losses by 11–55% compared with fallow ground. Oats performed the best at earlier sowings, closely followed by triticale, while Italian ryegrass performed better at the later sowing. Sowing in March resulted in the highest reduction in N losses for all species. These results demonstrated that catch crops can be used to reduce N losses in these Waikato systems, and that species selection and sowing date are key to maximise their effectiveness. [ABSTRACT FROM AUTHOR]

A lysimeter experiment using undisturbed monoliths from a stony silt loam soil was carried out to quantify the effects different pasture types on N losses from urine applied to soil on different dates. Three pasture types were tested: (a) perennial ryegrass (Lolium perenne)/white clover (Trifolium repens) (PRG/WC), (b) perennial ryegrass/white clover/plantain (Plantago lanceolata) (PRG/WC/P) and (c) Italian ryegrass (Lolium multiforum)/white clover/plantain (IRG/WC/P), with four different urine applications dates (late summer, early autumn, mid‐autumn and late autumn). Cattle urine was applied at the equivalent of 700 kg N−1 ha−1. There was a significant reduction in total amount of nitrate (NO3−‐N) leached under the PRG/WC/P (14% reduction) and IRG/WC/P (24% reduction) compared with the PRG/WC. High NO3−‐N leaching losses were found at each urine application date (>181 kg NO3−‐N/ha), suggesting there may be higher than expected N leaching losses when urine is deposited onto shallow stony soils, during warmer months (late summer and early autumn). There was no significant interaction between pasture type and urine timing on NO3−‐N leaching losses. [ABSTRACT FROM AUTHOR]

Future development pathways for irrigated dairy farms in Canterbury operating under stricter nitrogen (N) loss limits were compared in two farmlets over four years. One represented the traditional pathway of intensification via higher inputs of N fertiliser and supplementary feed ('higher input-high efficiency', HI-HE), while the other represented a lower input pathway using half the amount of N fertiliser and one quarter the amount of supplementary feed ('lower input-high efficiency', LI-HE). The stocking rate of both systems was matched to feed supply to achieve high utilisation (∼90%) of the pasture grown. Mean total annual N surplus and estimated nitrate-N leaching were lower in LI-HE than HI-HE, by 46% and 25% respectively. Milk production was lower for LI-HE (1,700 kg versus 2,240 kg milk fat + protein per ha/year). Estimated profit was the same for both systems at a milk price of $6.46/kg fat + protein, below which LI-HE was more profitable than HI-HE and vice-versa. Compared with the benchmark high-performing Lincoln University Demonstration Dairy Farm (LUDF) through the same period, LI-HE was 2% less profitable, but estimated N leaching was ∼30% lower. Subsequent adoption of the LI-HE system by LUDF demonstrated that the system is scalable, and profitable. [ABSTRACT FROM AUTHOR]

A lysimeter experiment was carried out to investigate the effects of applying readily available carbon (12 or 24 t sucrose ha−1) to soil on nitrogen (N) losses from cattle urine patches. The carbon (C) was readily available to microbes and was applied onto intact soil monolith lysimeters, containing stony silt loam soil, beneath either ryegrass (Lolium perenne)/white clover (Trifolium repens) pasture (RG/WC) or lucerne (Medicago sativa). Cow urine (700 kg N ha−1) was applied in early July 2017, two days after C application. The application of readily available C increased the immobilisation of N in the soil which reduced the amount of soil mineral N. The C-induced immobilisation of N reduced the ammonia oxidising bacteria population growth rate and the amount of nitrate leached by 51–89%. The addition of readily available C had no significant effect on nitrous oxide emissions. These findings were consistent under both RG/WC and lucerne. [ABSTRACT FROM AUTHOR]

Nitrate leaching from soil is a major problem in New Zealand pastoral systems, requiring development of practical methods to manage accumulation of nitrates. Nine feed trials were carried out in the Waikato (n = 3) and in Canterbury (n = 6) between 2013 and 2016; from which 424 samples were selected for forage quality testing. Only tick beans and forage rape met the lactating feed criteria for adequate crude protein (CP; > 16% DM) and soluble sugars and starch (SSS; > 25% DM). When an 'environmental' criterion was added to a feed value for lactating cows this reduced the options to fodder beet only. However, the CP measurements for fodder beet were suboptimal for milk production, requiring the fodder beet to be mixed with high protein feeds such as pasture or pasture silage. The lower protein requirements for non-lactating cows, including an additive environmental criterion enabled a wider range of feeds to be considered e.g. kale, sunflowers and swedes in Canterbury (12 entries) and fodder beet and rape in the Waikato (21 entries). Addition or restriction of nitrogen fertiliser was the only agronomic management intervention that consistently altered animal feed quality and potentially changed N excretion. Crop choice was likely to have the greatest impact at the farm level. By limiting feed quality assessment to CP, SSS and their ratio (SSS:CP) we were able to define a selection/feed monitoring method to minimise N content of feed, maximise SSS feed value and limit excess N intake to reduce the nitrate leaching risk. [ABSTRACT FROM AUTHOR]